MAVIS: mechanical design and prototyping of the adaptive optics module toward the FDR

MAVIS is a Multi-Conjugate Adaptive Optics for the UT4 of VLT designed to deliver a corrected FoV to a spectrograph, an imager, and a visiting instrument. An optical bench, kinematically mounted on the overall main structure (OMS) is used to support the post focal relay optics, which include the ADC, a K-mirror, the DMs, the calibration, and the selectors. Said bench also rigidly supports the LGS module, the NGS module and the imager. The design and analysis of the steel bench is presented together with the design, analysis, and prototyping of the optomechanical elements. Particular attention is given to the evolution of the derotation system design (K-mirror), which has been strongly improved, and to its prototyping.